fs: ramfs: file-nommu: add SetPageUptodate()
Bob Liu [Wed, 11 Jul 2012 21:02:35 +0000 (14:02 -0700)]
commit fea9f718b3d68147f162ed2d870183ce5e0ad8d8 upstream.

There is a bug in the below scenario for !CONFIG_MMU:

 1. create a new file
 2. mmap the file and write to it
 3. read the file can't get the correct value

Because

  sys_read() -> generic_file_aio_read() -> simple_readpage() -> clear_page()

which causes the page to be zeroed.

Add SetPageUptodate() to ramfs_nommu_expand_for_mapping() so that
generic_file_aio_read() do not call simple_readpage().

Signed-off-by: Bob Liu <lliubbo@gmail.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: David Howells <dhowells@redhat.com>
Cc: Geert Uytterhoeven <geert@linux-m68k.org>
Cc: Greg Ungerer <gerg@uclinux.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

fs/ramfs/file-nommu.c

index fbb0b47..d5378d0 100644 (file)
@@ -110,6 +110,7 @@ int ramfs_nommu_expand_for_mapping(struct inode *inode, size_t newsize)
 
                /* prevent the page from being discarded on memory pressure */
                SetPageDirty(page);
+               SetPageUptodate(page);
 
                unlock_page(page);
                put_page(page);